Server-Side Form Validation Using Expressions

This example demonstrates how you can build a validation expression that processes user input on the server side. You need to register a custom function that can be used in expressions. Such a function can query the server. SurveyJS also allows you to validate input in an event handler. This article explains the difference between server-side input validation using expressions and an event handler. Select React, Vue, Knockout, jQuery, or Angular to view an example for your JavaScript framework of choice. Read more...